Corpus of Electronic Texts Edition

An Irish Astronomical Tract (Author: [unknown])

Chapter 20

NECESSARIO IGITUR FATENDUM EST..

It must he admitted that the size of the sun is greater than that of the earth, and that the shadow of the earth never extends up beyond the sphere of Mercury. The shadow of the earth is conical in shape, with the base towards the earth, while it becomes narrower by degrees, until it comes to an end a little above the sphere of the moon. The same shadow obscures the moon according as it spreads over it; for when the moon is in the north or south of the shadow, it obscures the portion of the moon on which it is, and when it spreads over half of the moon, the shadow obscures it completely. However, we know, and we have found it written, that that shadow of the earth does not reach the stars nor any of the planets, but only the moon which is neighbour to the earth, and therefore all the planets, except the moon, and the stars borrow light from the sun always; and thus he84 proves that the sun is much larger than the earth, as this figure below shows.